In test firings of MK-46 Torpedoes, failures sometime prevent the engine from running property. Back-up safety devices and methods have been developed to aid in recovering a torpedo which has failed during operation. In particular, electronic and mechanical means have been designed to control the torpedo's operation for preventing it from going below select depths, and also to release weight systems in order to allow the torpedo to return to the surface for retrieval.
Presently, there are two principal circuits being used to eject lead weights from a failed torpedo. The depth cutoff (DCO) circuit is activated whenever the torpedo reaches a preset depth. Unfortunately, to prevent interference with the tests, the DCO depth must usually be set quite deep where high pressure could cause other system failures. Also, the time required after failure for the torpedo to sink to DCO depth, then rise to the surface, could permit the torpedo to drift out of range of the recovery crew.
The second lead weight ejection circuit in current operation, is the Power Failure Circuit. This circuit ejects the lead weights if, after the engine has run approximately ten seconds or more it then stops. However, if the engine fails within the first ten seconds, the circuit does nothing.